The present invention provides novel bis(aminophenoxy)-alpha-substituted stilbenes which are useful for curing epoxy resins. Epoxy resins are well established as a class of curable compositions which find efficacy in a myriad of applications. The curing of epoxy resins is effected by a wide range of curing agents including, for example, the primary and secondary aliphatic, cycloaliphatic and aromatic polyamines; dicarboxylic acids and the anhydrides thereof; aromatic hydroxyl containing compounds; imidazoles; guanidines; ureaaldehyde resins and alkoxylated derivatives thereof; melamine-aldehyde resins and alkoxylated derivatives thereof; amidoamines; epoxy resin adducts; and various combinations thereof. In many of the applications served by epoxy resins, it would be desirable to improve one or more of the physical and/or mechanical and/or thermal properties of the cured products thereof. The bis(aminophenoxy)-alpha-substituted stilbenes of the present invention are also of useful for preparation of other thermoset polymers, such as, for example, polyurethanes and polyureas.
The bis(aminophenoxy)-alpha-substituted stilbenes of the present invention possess a unique molecular structure heretofore unavailable in an epoxy resin curing agent. One of the features of the molecular structure inherent to the bis(aminophenoxy)-alpha-substituted stilbenes of the present invention is the alpha-substituted stilbene moiety which is a mesogen, especially when 4,4'-disubstitution predominates. A second feature of the molecular structure inherent to the bis(aminophenoxy)-alpha-substituted stilbenes of the present invention is the presence of an ether linkage between each aromatic ring of the alpha-substituted stilbene moiety and each aromatic ring of the aminoaryl group. These ether linkages provide flexibility, thus decoupling the aromatic rings possessing the amino groups from the mesogenic moiety (alpha-substituted stilbene). A third feature of the molecular structure inherent to the bis(aminophenoxy)-alpha-substituted stilbenes of the present invention is the presence of the amino groups on the aromatic rings which are decoupled from the mesogenic moiety via the ether linkages, such that the amino group may be present at any position on the decoupled aromatic ring. Variation of the amino group substitution on the aromatic rings leads to a high degree of control over the type of liquid crystallinity achievable in certain of the curable compositions prepared therefrom and, surprisingly, liquid crystallinity can still be achieved even with ortho substitution by the amino group. The combination of molecular structures inherent to the bis(aminophenoxy)-alpha-substituted stilbenes of the present invention provides curable epoxy resin compositions with outstanding processability and cured epoxy resin compositions thereof with substantial improvements in one or more physical and/or mechanical and/or thermal properties.